In particular, I am optimistic about humanity's prospects for starting exemplary new collaboratively developed knowledge resources. When we hit upon the correct models for collaborative knowledge-collection online, there will be a jaw-dropping, unprecedented, paradigm-shifting explosion in the availability of high-quality free knowledge.

In particular, I am optimistic about humanity's prospects for starting exemplary new collaboratively developed knowledge resources. When we hit upon the correct models for collaborative knowledge-collection online, there will be a jaw-dropping, unprecedented, paradigm-shifting explosion in the availability of high-quality free knowledge.

A few years ago, I wrote a short book entitled 'Our Final Century'. I guessed that, taking all risks into account, there was only a 50 per cent chance that civilisation would get through to 2100 without a disastrous setback. This seemed to me a far from cheerful conclusion. However, I was surprised by the way my colleagues reacted to the book: many thought a catastrophe was even more likely than I did, and regarded me as an optimist. I stand by this optimism....

I am optimistic about human relationships - in particular, about friendship. Perhaps you have heard gloomy predictions about friendship: it's dying out, people no longer have friends they can confide in, loneliness is on the rise....

The full-length versions of these pieces (and many more) can be found at www.edge.org[9], a website founded by John Brockman.'What Is Your Dangerous Idea?', by John Brockman (Editor), is published by Simon & Schuster, £12.99; 'What We Believe But Cannot Prove', by John Brockman (Editor), is published by Pocket Books, £7.99